Complex electronic designs are driving innovation across many industries today. Digital Storage Oscilloscopes (DSO) and high-speed Data Acquisition Systems (DAS) are basic tools for designing, manufacturing and repairing electronic equipment. As the eyes of the engineer, oscilloscopes and DAS's are the key to meeting today's demanding measurement challenges. An oscilloscope or DAS acquires and stores electrical waveforms and can display that analog signal's amplitude and frequency content. This information can reveal a high-speed phenomenon that is too fast for the eyes, help determine whether a malfunctioning component is distorting a signal, how much of a signal is noise, whether the noise changes with time, and more.
The oscilloscope's fundamental ability to accurately measure an analog signal is determined simultaneously by several factors. Those include the voltage amplitude range, the voltage resolution, the maximum analog frequency (or analog bandwidth), and the digitizer sampling rate (also known as bandwidth). When an oscilloscope's analog bandwidth and/or sampling rate is too low for the analog signal that is being captured, the oscilloscope will not be able to resolve high-frequency content and rapid amplitude changes. If the oscilloscope's voltage resolution is not high enough, the amplitude content of the analog signal will be distorted and the low-level details of the signal will be suppressed below the background and quantization noise floor. That information will be lost and the acquired signal rendered unusable, particularly for non-repetitive signals or unique transient signal events.
In general, oscilloscopes can accurately resolve the amplitude of a constant-frequency, sinusoidal wave signal up to a significant fraction of the analog bandwidth of the oscilloscope. Above that frequency, the amplitude accuracy decreases with increasing frequency. Entry-level oscilloscopes typically have a maximum analog bandwidth of 100 MHz which yields satisfactory sinusoidal accuracy up to 20 MHz. For digital signals, such as a square wave, oscilloscopes must capture an analog bandwidth much higher than that required by a sinusoid wave. Square waves include all odd harmonics of the fundamental square wave frequency. The oscilloscope must be able to acquire the first, third, fifth, seventh, and ninth harmonics of the square wave signal or the displayed waveform will lose key features and may not be enough to represent the original signal. Capturing high-speed digital, serial communications, video and other complex signals can require oscilloscope analog bandwidths of 500 MHz or more.
Unfortunately, oscilloscopes having a high bandwidth can be cost prohibitive. Further, oscilloscopes having both a high bandwidth and a high voltage resolution are even more costly, rare, or even unavailable within the current state-of-the-art. Furthermore, an oscilloscope requires a probe to obtain the electrical signal from a device-under-test (DUT) before it is acquired and recorded. Probes that are useful for measuring large voltage or large current signals do not typically offer the high-frequency bandwidth to accurately measure rapid amplitude changes. Probes that have high bandwidths that are useful for measuring fast signals with rapid amplitude changes, often cannot tolerate voltages higher than 1 volt without the use of an attenuator which may introduce amplitude and frequency distortions.